One of the modern adjuncts to culinary processing in the home is the pressure cooker, usable to prepare food for the table and for preserving food by canning. Such a cooker conventionally consists of a vessel or receptacle having an open top through which water and material to be treated are loaded, the top being afterwards closed by a cover which is releasably sealed vaportight to the receptacle. This produces a closed container in which steam pressure develops upon application of heat to effect the cooking process, to result in a superpressure condition in which the steam pressure within the cooker exceeds the pressure ambient to the cooker.
Conventionally, the cover of such a cooker is provided with a vertical vent pipe on which loosely rests a weight to regulate the pressure developed in the cooker during the cooking process. Such cookers commonly also contain a pressure release plug, usually in the cover, which is designed to be ejected to relieve pressure within the cooker before it reaches a dangerous level.
It is known to provide the cover and the receptacle with circumferentially spaced lugs at their peripheries, which may be interengaged by relative rotation therebetween to produce a sealing engagement of the cover and receptacle against a resilient sealing ring or gasket, so as to effect the vapor-tight seal of the cooker which is requisite to pressure cooking or canning. Special lug configurations are known which produce the seal mechanically, and special configurations of sealing rings are known whereby the development of pressure in the closed cooker acts pneumatically to maintain the seal formation.
Pressure cookers including the described type are used by persons of varying skills and understandings of the operation of the pressure cooker, and who, on occasion, may incompletely or improperly secure the cover to the cooker body. Experience has indicated that a substantial risk exists that the cover may be blown from the cooker should the cover through carelessness or otherwise be incompletely locked to the cooker body. This could occur becuase, when closing the cover on the cooker, the cover lugs were imperfectly engaged beneath the receptacle lugs. A potential hazard also exists when an attempt is made prematurely to rotate the cover and remove it before the cooker pressure has been reduced to a safe level.